Objective To isolate and identify Orientia tsutsugamushi from rodents in Dali city, Yunnan province, China, and to amplify and analyze its full-length 56 kDa type-specific antigen (TSA) gene. Methods From August 2020 to August 2021, rodents were collected from four townships in Dali city using the night trapping method. Nested polymerase chain reaction (PCR) was used to amplify the conserved sequence of O. tsutsugamushi. PCR-positive samples were taken to intraperitoneally inoculate mice to isolate O. tsutsugamushi. The isolated O. tsutsugamushi was identified by observation with Giemsa staining and indirect immunoassay. Primers were designed to amplify the full-length 56 kDa TSA gene of O. tsutsugamushi. Bioinformatics software (MEGA Ⅹ, DNAStar 7.1, and SeqMan) was used for homology and phylogenetic analyses. Results A total of 76 rodents were captured, including 6 species under 5 genera. PCR detected the sequence of O. tsutsugamushi from the liver and spleen tissue homogenate of a Rattus tanezumi, with a positive rate of 2.38% (1/42). One strain named DALIV8 was isolated and identified as O. tsutsugamushi. The full-length 56 kDa TSA gene of this isolate was 1 566 bp, encoding 521 amino acids (GenBank:OM914742). The 56 kDa TSA gene of the DALIV8 strain showed similarities of 82.30%-98.85% at the nucleotide level and 74.04%-98.28% at the amino acid level to the Kawasaki, Boryong, Karp, Kato, and TA763 genotypes. So, the isolate was identified as the TA763 genotype. Conclusion The DALIV8 strain isolated from R. tanezumi in Dali city is firstly recorded as the TA763 genotype of O. tsutsugamushi in Yunnan province, China.
KONG Yi-chen, TIAN Jia-wei, YANG Zi, YIN Hong-min, HUANG Hao, CHEN Li, ZHANG Yun-zhi
. Isolation, identification, and 56 kDa type-specific antigen gene characterization of Orientia tsutsugamushi from Rattus tanezumi in Dali, Yunnan province, China[J]. Chinese Journal of Vector Biology and Control, 2022
, 33(4)
: 503
-509
.
DOI: 10.11853/j.issn.1003.8280.2022.04.012
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